Withdrawn Provided for Historical Reference Only 2-BUTANONE (METHYL ETHYL KETONE) Method no.: 16 Matrix: Air Target concentration: 200 ppm (590 mg/m3) (OSHA PEL) Procedure: Collection on silica gel, desorption with DMSO, and analysis by gas chromatography with a flame ionization detector. Recommended air volume and sampling rate: 3 L at 0.1 L/min Detection limit of the overall procedure: 1.4 ppm (4.0 mg/m3) Reliable quantitation limit: 1.5 ppm (4.3 mg/m3) Standard error of estimate at the PEL: 5.9% (Section 4.6.) Special requirements: Samples are collected on 2 silica gel tubes in series. The second tube is used as a backup for the first tube. Status of method: Evaluated method. This method has been subjected to the established evaluation procedures of the Organic Methods Evaluation Branch. Date:WITHDRAWN January 1980 Chemist: Carl J. Elskamp Organic Methods Evaluation Branch OSHA Analytical Laboratory Salt Lake City Utah Note: OSHA no longer uses or supports this method (December 2019). Withdrawn Provided for Historical Reference Only 1. General Discussion 1.1. Background 1.1.1. History MEK (Methyl Ethyl Ketone) samples analyzed at the OSHA laboratory have normally been collected on activated charcoal and analyzed by gas chromatography after desorption with carbon disulfide as described in NIOSH Method S3 (Ref. 5.1.). It was found by a later study that MEK was not stable on coconut shell charcoal, especially when the vapor samples were collected at high humidity and also when the samples were stored at room temperature (Ref. 5.2.). Since the OSHA laboratory analyzes a large number of MEK samples (more than 4300 MEK samples were analyzed in fiscal year 1979) and a stability problem has been established for samples collected using the NIOSH method, it was necessary to find a more suitable method of collection. Several different solid adsorbents were tested for breakthrough. Among those tested that gave unsatisfactory breakthrough volumes were: Chromosorb 101, Chromosorb 102, Chromosorb 103, Chromosorb 104, Chromosorb 105, Chromosorb 106, Chromosorb 107, Chromosorb 108, XAD-2 resin, Alumina, Tenax, Porapak P, and Chromosorb 102 coated with 15% SP2401. These adsorbents exhibited a relatively low capacity under the following test conditions: MEK concentration - 1176 mg/m3, relative humidity - 80%, sampling rate - 0.2 L/min, amount of solid adsorbent - the same volume as the front section of a 150-mg charcoal tube. This study does not rule out the possible use of these adsorbents, but collection tubes would have to be made larger to increase the capacity or sampling rates would have to be lowered so an integrated sample could be taken over a reasonable time. Since it is desirable to use a small sampling device and the sampling pumps presently used for field sampling have a minimum sampling rate of 0.05 L/min, these solid adsorbents were not acceptable. The only solid adsorbents found suitable for collection besides coconut shell charcoal were petroleum-base charcoal (SKC Lot 104) and silica gel. These two adsorbents were evaluated according to the evaluation scheme used by the Organic Methods Evaluation Branch. The analytical procedure was essentially NIOSH Method S3 for the Lot 104 charcoal samples and an adapted method (Ref. 5.3.) using DMSO as the desorption solvent for the silica gel samples. The silica gel collection is the recommended method of choice since samples are more stable if collected this way. Charcoal should not be used unless absolutely necessary. If charcoal is used, the samples must be refrigerated immediately after sampling and during shipment to the laboratory. Data for both procedures is included in this report. Data for the Lot 104 charcoal tube method is given in Section 4.8. 1.1.2. Toxic effects (This section is for information only and should not be taken as the basis for OSHA policy.) MEK may be irritating to eyes, mucous membranes, and in high concentrations, narcotic. (Ref. 5.4.) MEK is similar to but more irritating than acetone. The vapor is irritating to mucous membranes and conjunctiva. No serious poisonings were reported in man except for dermatitis. (Ref. 5.5) Dermatitis can result if excessive repeated prolonged skin contact occurs. Minor skin contacts have been shown to cause no evidence of irritation. (Ref. 5.6.) MEK can be recognized at 25 ppm by its odor, which is similar to acetone but more irritating. The warning properties prevent inadvertent exposure to toxic levels. (Ref. 5.7.) The TLV was established at a level to prevent injurious effects and minimize complaints about odor and irritation. (Ref. 5.8.) 1.1.3. Operations where exposure occurs MEK is mainly used as a solvent for formulations of nitrocellulose. (Ref. 5.9.) It is also used as a solvent in fabric coating, the manufacture of colorless synthetic resins, the manufacture of smokeless powder, the surface coating industry, the manufacture of WITHDRAWNartificial leather, the lacquer and varnish industry, pharmaceuticals and cosmetics, the manufacture of synthetic rubber, production of lubricating oils, vinyl coatings, adhesives, acrylic coatings, hardwood pulping, the manufacture of ink, and lube oil de-waxing by solvent extraction. (Ref. 5.10.) Note: OSHA no longer uses or supports this method (December 2019). Withdrawn Provided for Historical Reference Only 1.1.4. Size of work population that are exposed NIOSH estimates that over 3 million workers are potentially exposed to MEK in the United States. (Ref. 5.9.) 1.1.5. Physical Properties (Ref. 5.4. and 5.11.) molecular weight: 72.10 boiling point: 79.6EC color: clear, colorless vapor pressure: 90.7 mmHg at 25EC flash point: 35EF odor: acetone-like specific gravity: 0.805 (20/4EC) lower explosive limit: 1.8% (by volume) molecular formula: CH3COC2H5 synonyms: 2-butanone, methyl ethyl ketone, MEK, ethyl methyl ketone 1.2. Limit defining parameters 1.2.1. Detection limit of the analytical procedure The detection limit of the analytical procedure is 12.1 ng per injection. The magnitude of the detection limit is due to an interference in DMSO. (Section 4.1.) 1.2.2. Detection limit of the overall procedure The detection limit of the overall procedure is 13.0 µg per sample (1.5 ppm/4.3 mg/m3). This is the amount of MEK spiked on a silica gel tube which allows recovery of an amount of MEK equivalent to the detection limit of the analytical procedure. (Section 4.2.) 1.2.3. Reliable quantitation limit The reliable quantitation limit is the same as the detection limit of the overall procedure since the recovery at this level is greater than 75% and the 95% confidence limit is within ±25%. (Section 4.3.) The reliable quantitation limit and detection limits reported in the method are based upon optimization of the instrument for the smallest possible amount of analyte. When the target concentration of an analyte is exceptionally higher than these limits, they may not be attainable at the routine operating parameters. 1.2.4. Sensitivity The sensitivity of the analytical procedure over a concentration range representing 335 to 1342 mg/m3 based on the recommended air volume is 140,800 area units per mg MEK/mL DMSO. The sensitivity is determined by the slope of the calibration curve. (Section 4.4.) The sensitivity will vary somewhat with the particular instrument and operating parameters used in the analysis. 1.2.5. Desorption efficiency The recovery of analyte from the collection medium must be 75% or greater. The average recovery over the range of 0.5 to 2 times the target concentration is 97.9%. (Section 4.5.) 1.2.6. Precision (analytical method only) The pooled coefficient of variation obtained from replicate determinations of analytical standards at 0.5, 1 and 2 times the target concentration is 0.0061. (Section 4.4.) WITHDRAWN1.2.7. Precision (overall procedure) The overall procedure must provide results at the target concentration that are ±25% or better at the 95% confidence level. The precision at the 95% confidence level for the 15-day storage test is ±12.2%. (Section 4.6.) This includes an additional ±5% for sampling error. Note: OSHA no longer uses or supports this method (December 2019). Withdrawn Provided for Historical Reference Only 1.3. Advantages 1.3.1. The sampling procedure is convenient. 1.3.2. The analytical procedure is sensitive and reproducible. 1.3.3. Reanalysis of samples is possible. 1.3.4. Samples are stable, even at room temperature. 1.3.5. It may be possible to determine other compounds simultaneously. 1.3.6. Interferences can be circumvented by proper selection of GC parameters. 1.3.7. The desorption solvent (DMSO) elutes later than most solvents normally analyzed for in industrial air. 1.4. Disadvantages 1.4.1. The amount of sample that can be taken is limited by the total milligrams the silica gel will adsorb before overloading. 1.4.2. The precision is limited by the reproducibility of the pressure drop across the tubes. The pumps are usually calibrated for one set of tubes only. 1.4.3. The desorption solvent (DMSO) elutes late, which increases the run time for analysis. 1.4.4. DMSO has trace contaminants that may be potential interferences under high sensitivity conditions. Under normal operating conditions, these contaminants pose no problem to analysis. 1.4.5. After repeated injections of DMSO, there is a build-up of residue formed in the collector of the detector. 2. Sampling Procedure 2.1. Apparatus 2.1.1. An approved and calibrated personal sampling pump whose flow can be determined within ±5% at the recommended flow. 2.1.2. Silica gel tubes: glass tube with both ends flame sealed, 70 mm × 6-mm i.d.